Electromagnetic clutch having ball ramp actuator and torsion spring

Abstract

An electromagnetic clutch for motor vehicle drive line applications includes a friction clutch pack, a ball ramp actuator and an electromagnetic coil. The ball ramp actuator includes a pair of circular members having opposed pairs of arcuate recesses receiving load transferring members and a torsion spring which provides a restoring force to return the circular members to their center, disengaged positions. Improved clutch control, particularly during disengagment, is achieved by this ball ramp actuator configuration.

1. A ball ramp clutch for a motor vehicle driveline comprising, in combination,
 an input member,  
 an output member,  
 a first circular member disposed for rotation with said input member and defining a first plurality of arcuate recesses and a first spring engaging feature,  
 a rotor,  
 a second circular member secured to said rotor, disposed adjacent said first circular member and defining a second plurality of arcuate recesses and a second spring engaging feature,  
 a plurality of load transferring members disposed in said recesses,  
 a torsion spring operably disposed between said first and said second spring engaging features of said circular members and,  
 a friction clutch pack assembly having a first plurality of friction discs secured for rotation with said input member and a second interleaved plurality of friction discs secured for rotation with said output member,  
 whereby relative rotation between said first circular member and said second circular member provides compressive force to said friction clutch pack.  
 
   
   
     2. The ball ramp clutch of  claim 1  wherein said torsion spring is rectangular in cross section and includes a pair of axially extending tangs. 
   
   
     3. The ball ramp clutch of  claim 2  wherein said spring engaging features of said circular members define slots for eceiving said tangs of said torsion spring. 
   
   
     4. The ball ramp clutch of  claim 1  wherein said torsion spring includes a plurality of coils. 
   
   
     5. The bail ramp clutch of  claim 1  further including an electromagnetic coil for retarding rotation of said rotor. 
   
   
     6. The ball ramp clutch of  claim 5  wherein said rotor partially surrounds said electromagnetic coil. 
   
   
     7. The ball ramp clutch of  claim 1  wherein said input member is a primary output shaft of a transfer case and said output member drives a secondary output of said transfer case. 
   
   
     8. An ball ramp clutch having a ball ramp operator comprising, in combination,
 an input member,  
 an output member,  
 a first member disposed for rotation with said input member and defining a plurality of ramped recesses and a first spring engaging feature,  
 a second member disposed adjacent said first member, said second member defining a second plurality of ramped recesses adjacent said first plurality of ramped recesses and a second spring engaging feature.  
 a torsion spring engaging said spring engaging features of said first and second members,  
 a plurality of load transferring members cooperatively disposed in opposed pairs of said ramped recesses,  
 means for retarding motion of said second circular member relative to said first circular member, and  
 a friction clutch pack operably disposed between said input and said output member and one of said circular members,  
 wherein relative rotation between said first and second members compresses said friction clutch pack and transfers torque from said input member to said output member.  
 
   
   
     9. The ball ramp clutch of  claim 8  wherein said means for retarding motion is an electromagnetic coil. 
   
   
     10. The ball ramp clutch of  claim 9  further including a rotor partially surrounding said electromagnetic coil. 
   
   
     11. The ball ramp clutch of  claim 8  wherein said torsion spring is rectangular in cross section and includes a pair of axially extending tangs. 
   
   
     12. The ball ramp clutch of  claim 11  wherein said spring engaging features of said first and second members define slots which receive said tangs of said torsion spring. 
   
   
     13. The ball ramp clutch of  claim 8  wherein said torsion spring includes a plurality of coils. 
   
   
     14. The ball ramp clutch of  claim 8  further including an armature disposed adjacent said rotor. 
   
   
     15. A motor vehicle transfer case comprising, in combination,
 a shaft adapted to provide drive energy to a primary driveline,  
 a secondary output for providing a drive energy to a secondary driveline, and  
 an electromagnetic clutch assembly having 
 a first circular member defining a plurality of ramped race sees disposed for rotation with said primary output and a first spring engaging feature,  
 a second circular member defining ramped recesses freely rotatable about said primary output shaft and a second spring engaging feature,  
 a torsions spring operably disposed between said spring engaging features of said first and said second circular members  
 a plurality of load transferring members disposed in said ramped recesses,  
 
 an electromagnetic coil for retarding motion of said second circular member, and  
 a friction clutch pack having an input coupled to said shaft and an output driving said secondary output.  
 
   
   
     16. The transfer case assembly of  claim 15  whereby energization of said electromagnetic coil compresses said friction clutch pack and transfers drive energy from said shaft to said secondary output. 
   
   
     17. The transfer case assembly of  claim 15  wherein said torsion spring is rectangular in cross section and includes a pair of axially extending tangs. 
   
   
     18. The transfer case assembly of  claim 17  wherein said spring engaging features of said circular members include slots which receive said tangs of said torsion spring. 
   
   
     19. The transfer case assembly of  claim 15  wherein said torsion spring includes a plurality of coils. 
   
   
     20. The transfer case assembly of  claim 15  further including a planetary gear speed reduction assembly adapted to drive said shaft.